meeting of the minds
n. when two parties to an agreement (contract) both have the same understanding of the terms of the agreement. Such mutual comprehension is essential to a valid contract. It is provable by the express provisions of a written contract, without reference to any statements or hidden thoughts outside the writing. There would not be a meeting of the minds if Bill Buyer said, "I'll buy all your stock," and he meant shares in a corporation, and Sam Seller said, "I'll sell all my stock to you," and meant his cattle.